1. Field of the Invention
The present invention relates to a polarized light illumination apparatus for uniformly illuminating a rectangular illumination area with light polarized in the same direction, and also to a projector using such a polarized light illumination apparatus. More particularly, the present invention relates to a structure for synthesizing lights emitted from two light sources such that the resultant synthesized light is polarized in the same direction.
2. Description of Related Art
In liquid crystal display devices using a modulating element such as a liquid crystal element which modulates light polarized in a particular direction, only one component of two different polarized light components included in light emitted from a light source is used. To obtain a projected image with high brightness, it is required to increase the utilization efficiency of light.
However, when a projector is constructed using a single light source, the utilization efficiency of light has a practical upper limit. Thus, one technique of projecting a high-brightness image is to increase the amount of light using a plurality of light sources.
However, if a plurality of light sources are arranged in a simple fashion, the overall area of the light source image becomes greater by a factor corresponding to the number of light sources. As a result, the angle of light (illumination angle) striking an illumination area also increases by a corresponding factor. This means that the amount of light per unit area is the same as that obtained with a single light source. In other words, the amount of light per unit area cannot be increased by using a plurality of light sources arranged in the above-described fashion.
Even when the amount of light can be increased by using a plurality of light sources, if only one component of two polarized light components of light emitted from the light sources is used, one-half of the total amount of light is wasted.